Luting compound



Patented Feb. 17, 1925.

HUGH BODMA N, 0F OAKMO-NT, PENNSYLVANIA.

LUTING COMPOUND.

mo Drawing. Application filed April 6,

T 0 all whom itmay concern.

Be. it known that 1, HUGE RoDMAN, a citizen of the United States, and a. resident of Oakmont, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Luting Compounds, of which the following is a specification.

This invention relates to materials for sealing the boxes used in carbonizing and annealing metal parts.

i The object of the invention is to provide a non-injurious material for sealing the boxes that are to be placed ina furnace for various heat treating processes. More particularly the object is to provide a material which will effectively seal the openings of such boxes, as for example the space between the mouth and lid thereof, the material being of such a character as to prevent, or not to cause, undue deterioration of the boxes and lids at the point of sealing. The uses and advantages of the material disclosed will be more apparent to those familiar with the art from the following specification.

In the heat treating of metal parts, as for example the carbonizing of gears, and other machined parts, preliminary to casehardening them, metal boxes withloosely fitting covers or lids are used as containers for the parts to be treated. These boxes are packed with the steel parts embedded in a carbonizing compound, or the like. The junction of the box with its cover or lid 1s then sealed or luted with fire clay to prevent the penetration into the box of the furnace gases during the heat treating operation. :This luting material is applied as a doughy mass, by hand, or with a trowel, and during the exposure inside the furnace, it burns to a hard clay product. After the box is removed from the furnace this clay is broken olf and is not re-used.

Carbonizing or annealing boxes were formerly made of cast iron or cast steel, but in later years, due to the excessive oxidation and scaling which takes place during the use of cast iron or cast steel boxes in red hot furnaces, certain alloys have been largely used for making the boxes. These are usuallyalloys of iron, chromium,'nickel, or other metals. Although such boxes cost a great deal more than mere cast iron or cast steel boxes, the-y are more economical in use because of their resistance to the oxidation 1922. Serial N0. 550,196.

and scaling resulting from the high fur-. nace temperatures to which they are exbing or scaling around the edge of the boxes has been generally considered to be due to some chemical action of the excess gases generated within the boxes during the heat treating of the contents. Investigations of this trouble, and the attempts to remedy it have usually taken the line of investigation of the carbonizing or other packing material placed in the boxes around the metal parts. The manufacturers of such boxes, the

makers of carbonizing and packing mate-H rials, and the heat treaters of steel using the two materials, have made efforts to overcome this difliculty, and to ascertain its cause. Certain carbonizing materials have been absolutely rejected by certain users, because they believed that as a result of their use carbonizing boxes deteriorated more rapidly than with other carbonizing compounds. Certain other companies have spent large amounts in developmg various expensive alloys and metal compounds from which. non-corrodible heat treating boxes could be made.

Apparently no one has heretofore discovered that the solution of this difficulty resides in the particular luting material to be utilized for sealing the boxes.

I have discovered that, although there is unquestionably a difference in degree in the amount of scabbing of heat treating boxes depending upon the materials packed therein, and upon the material from which the a box is made, there is a much larger difference in this respect due to the character of sealing or luting material employed. I have further discovered that by utilizing a proper luting material the scabbing of the metal boxes at the point of sealing, and ordinarily considered due to the escape of gases therethrough, may be entirely prevented. This is true with any kind of metal boxes, even the cheaper cast iron and cast steel boxes, and no matter what packing material is used. The latter will, of

course, scale oif over their entire exterior surface, which determines their length of life, but the local 'scabbing at the edges will be prevented by the use of a proper luting material.

By adding a small percentage of a calcium compound, such for example as lime hydrate or lime carbonate, to ordinary fire clay, and making the resulting mixture into av suitable luting consistency by the addition of water, a sealing material is provided that prevents, or does not produce, any scabbi'ng at the point of sealing as has heretofore been the case. It is preferred to utilize finely powdered lime stone in a dry form, mixing thiswith a dry clay in proper proportions. The resulting mixture may be shipped dry and'made up into a luting paste as desired-by the ultimate consumer. Or, the lime compound, or limestone, can be added to the moist clay and mixed by any suitable means, as it is desired for use.

The amount of the calcium compound necessarily added to the clay depends somewhat upon the character of the latter material. For ordinary fire clays'the addition of 10% by weight 'of powdered limestone is sufficient to neutral zeits tendency to cause scabbing. The amount, however, may be varied widely, with good results.

Y'Vet clay when used as a luting for this purpose has a tendency to splinter off in small fragments at the edges ofth'e boxes, after they are placed in the hot furnace with the clay still wet. This tendency ap pears to be increased by the addition of lime compounds. To counteract this, I may add a small amount of organic binding material, such for example as flour. T have found that the addition of about 5% by volume of ordinary wheat flour along with the 10% by weight of powdered limestone to an ordinary fire clay, makes a highly ellicient material, having no disadvantages because of the addition of the 'lime, and hav ing the great advantage that it absolutely counteracts the tendency of the edges of the boxes to scab off during the heat treating exposure in a furnace. 7

I believe that certain other compounds may be added to the clay,as substitutes'for lime, with equally good results. For example, zirconia, or magnesite, which areno'n-fiuxing basic refractory compounds, may possibly be used. Certain other refractories, such, for example as silica, are distinctly 'liarinful, tend ng to increase the formation of scabs at the point of luting. Lime,'being widely available and comparatively cheap, is thepreferred material for adding to the ordinarily used fire clay. Although I am notprepared to give any fully determined explanation of the results produced by the addit on of a basic material like lime to the luting clay, and am not certain of't'heexact cause of formation of scabs when only ordinary clay is used as a lute, I have thoroughly tested the use of fire clay and lime, and find that as a matter-of fact itcompletely obviates the ditliculties referred to.

This advantage does not only occur where this particular luting IDZItQLZIl is used with alloy boxes, since it lengthens the life of the ordinary cast iron boxes as well. However, the life of an alloy box is so much longer than that of an iron box, due to the exteriorscaling of the latter over its'entire surface, that it is chiefly n connection with the alloy boxes that this invention shows to great advantage. These latter boxes have heretofore been limited'in life almost entirely by this scaling at the luting point.

An incidental advantage of the use of lime mixed with the luting clay is that when small pieces of the burnt clay become mixed in with carbonizing or annealing materia'l, as invariably results when the latter surface and soft uncarbonized spots are formed on the steel. This danger is materially reduced by the addition of lime to the luting clay.

I claim:

1. A luting material for sealing heattreating boxes, comprising clay and an added basic compound.

2. A luting material for sealing heat treating boxes, comprising clay and a basic compound added thereto which'will prevent scaling of the boxes at the point where the luting is applied.

8. A luting material for sealing heattreating boxes, comprising clay and a lime compound added thereto.

4:. A luting material for sealing heattreating boxes, comprising a mixture of clay with a basic material and an organic'binder. 5. A. luting material for sealing heattreating boxes, comprising a mixture of clay with a basic material and flour.

6. A material for sealing on the lids of heat-treating boxes, comprising ordinary fire clay, a lime compound, and an organic binder.

7. A material for sealing on'the lids of heat-treating boxes, comprising ordinary fire clay, a lime compound, and'fiour;

8. The method of preventing scaling of the edges of heat-treating boxes and their lids, comprising the luting thereof with a clayand lime mixture.

9. The method of preventing-'scaling-of the edges of heat-treating boxes and their lids, comprising the luting thereof with a mixture of clay and a basic compound.

10. The method of preventing scaling of the edges of heat-treating boxes and their lids, comprising the luting on of the lids with a mixture of clay, a basic compound and flour.

11. The method of preventing scaling of the edges of heat-treating boxes and their covers, comprising the luting on of the covers with a mixture comprising a basic compound and an organic compound.

12. The method of preventing scaling of the edges of heat-treating boxes and their lids, comprising the luting on of the lids with a mixture containing a basic compound and flour.

13. The combination with a. metal box for containing articles during heat treatment of a luting material comprising a basic compound.

14. .The combination With a metal box for containing articles during heat treatment of a luting material comprising afire clay and a basic compound added thereto.

15. The combination with a metal box for containing articles during heat treatment of a luting material comprising a fire clay and a lime compound.

16. The combination with a metal box for containing articles during heat treatment of a luting material comprising a fire clay, a basic compound, and an organic compound.

17. The combination with a metal box for containing articles during heat treatment of a luting material comprising a. fire clay a basic compound, and flour.

18. The combination with a metal box for containing articles during heat treatment of a luting material comprising a fire clay, a lime compound and flour.

In testimony whereof, I sign my name.

Jo. BAILY BROWN. 

